Phenolic profiles, antioxidant capacity, and acetylcholinesterase inhibitory activity of eight South African seaweeds Kannan R. R. Rengasamy & Stephen O. Amoo & Adeyemi O. Aremu & Wendy A. Stirk & Jiří Gruz & Michaela Šubrtová & Karel Doležal & Johannes Van Staden Received: 2 April 2014 /Revised and accepted: 15 October 2014 # Springer Science+Business Media Dordrecht 2014 Abstract In the search for new, safe, and natural sources as antioxidant and acetylcholinesterase (AChE) inhibitors, eight seaweeds were collected from the intertidal region in KwaZu- lu-Natal, South Africa and screened. Their total phenolic, flavonoid, and condensed tannin contents were determined, and the specific phenolic acids were identified. The highest total phenolics, flavonoids, and condensed tannin were re- corded in Rhodomelopsis africana (7.89 mg gallic acid equiv- alents g -1 ), Halimeda cuneata (3.64 mg catechin equivalents g -1 ), and Codium duthieae (0.60 mg cyanide chloride equiv- alents g -1 ), respectively. Based on UHPLC-MS/MS, different concentrations of protocatechuic acid, p-hydroxybenzoic acid, and m-hydroxybenzoic acid were quantified in the seaweeds. The highest radical scavenging ability and oxygen radical absorbance capacity (ORAC) were observed in red Gelidium foliaceum (52.2 %) and green C. duthieae (44 μmol TE g -1 ), respectively. In terms of AChE inhibition, the green H. cuneata exhibited greatest bioactivity (IC 50 = 70 μg mL -1 ). Overall, the findings suggest that these sea- weeds could be potential candidates as new sources of natural antioxidant and AChE inhibitors. Keywords Alzheimer’ s disease . AChE inhibitors . Phenolics . Macroalgae . UHPLC-MS/MS Introduction Seaweeds are a living renewable resource that rich in poly- phenols, polysaccharides, proteins, and vitamins as well as having antioxidant activity. Their phytochemical properties elevate their potential value for the pharmaceutical industry (Yan et al. 1998; Ganesan et al. 2011). Seaweed extracts have various pharmacological properties including antioxidant (Kumar et al. 2011; Kannan et al. 2013a), antimicrobial (Stirk et al. 2007), anticancer, antinociceptive (De Souza et al. 2009 ), photoprotective (Guinea et al. 2012 ), anti- inflammatory (De Souza et al. 2009), antiacetylcholinesterase (Stirk et al. 2007; Kannan et al. 2013b); antidiabetic (Kannan et al. 2013a), and antiviral (Hudson et al. 1999) activities. The coastline of South Africa has approximately 800 spe- cies of seaweeds with the south coast having the highest seaweed diversity (between 205 and 300 species), as com- pared to the east and west coasts (Bolton and Stegenga 2002). Thus, there is a huge potential to screen a diversity of seaweed species for novel compounds of pharmaceutical value. In South Africa, seaweeds are one of the least studied groups of plants, being mainly used for industrial production of alginate, abalone food, and fertilizers (McHugh 2003). Antioxidant compounds constitute a major component of clinical and experimental drugs that are currently considered for the prevention of neurodegenerative diseases (Moosmann and Behl 2002). The inhibition of acetylcholinesterase (AChE) is one of the most important approaches for the treatment of Alzheimer’ s disease (AD). This approach plays a critical role in enhancing the cholinergic neurotransmission in the brain and decreases the ß-amyloid formation in order to protect neurons from degeneration (Hodges 2006). Many marine algal species are known to exhibit potent antioxidant and anticholinesterase activities due to their polyphenol con- tent including flavonoids and tannins (Yoshie et al. 2002; Pangestuti and Kim 2011; Dellai et al. 2013). Despite K. R. R. Rengasamy : S. O. Amoo : A. O. Aremu : W. A. Stirk : J. Van Staden (*) Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa e-mail: rcpgd@ukzn.ac.za J. Gruz : M. Šubrtová : K. Doležal Laboratory of Growth Regulators & Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University & Institute of Experimental Botany AS CR, Šlechtitelů 11, 783 71 Olomouc, Czech Republic J Appl Phycol DOI 10.1007/s10811-014-0438-8